The methods employed in manufacturing broaching tools have remained relatively static over the past forty years or so.
In one manufacturing method, the broach is produced from high steel bar stock by first turning the bar in the soft condition (annealed condition) in a manual lathe operation to form the puller portion adjacent one end of the bar, the retriever portion adjacent the other end and the toothed cutting portion, including a roughing section, semi-finishing section and finishing section, intermediate the puller and retriever portions. Each cutting section includes sequentially arranged cutting teeth having a uniform cutting edge and predetermined increase in tooth size along the length of the cutting portion. In the manual lathe operation, the puller portion, retriever portion and toothed cutting portion are machined to within 0.30-0.050 inch of finished dimension. The so-called gullet radius and hook angle of the cutting teeth are turned in true relation with each other in the manual lathe operation.
Thereafter, the rough turned broaching tool is heat treated to a hardness of R.sub.c 65 and the cutting edges of the teeth are brought up sharp from the gullet radius manually using a broach sharpening machine designed specifically for this purpose. Then, the external diameters of the broaching tool are brought to finish size by an O.D. grinding operation. The total manufacturing time for a typical round broach employing these steps has been on the order of 8-9 hours and is very manual labor intensive.